Ablation therapy, such as radio frequency ablation (RFA), is commonly used medical procedure in which body tissue is ablated, shrunk, heated, coagulated, or otherwise treated using energy (for example, radio frequency energy). Common examples of ablation therapies include the treatment of cardiac arrhythmia, tumor destruction, pain amelioration, and controlling bleeding. Radio frequency ablation devices, for example, may include a power source and/or RF generator, and one or more ablation elements or electrode coupled to the power source.
The efficacy of RFA and other ablation therapies may depend on such parameters as the type of tissue being treated, the tissue depth to which the RF energy reaches, and the type and spacing of electrodes used. Also, because ablation typically affects tissue at a depth beneath the tissue surface, it can be difficult to accurately analyze the outcome of ablation treatments, including visualization of the ablation pattern and ablation tissue depth. Further, using tissues such as non-living porcine or cadaver tissues can produce a wide variation in results because of the non-uniformity of the samples and the subjective interpretation of results. The effectiveness of ablation therapies using these methods may only be assessed after cutting, staining, and subjectively observing the test tissue. All of these factors can make testing new ablation devices and methods costly and inaccurate. Tissue phantoms provide uniform characteristics and are sometimes used as substitutes for biological tissue, the properties of which can differ substantially from sample to sample. For example, heart phantoms may be used for analysis of cardiac motion and freezing properties of cardiac tissue; lung phantoms may be used for calibration of medical CT scanners; and entire phantom torsos, including organs, maybe used for laparoscopic technique training. However, just like biological tissue, it is not always easy to visualize the effects on these tissue phantoms of the medical or testing procedure. Also, many commonly used tissue phantom materials, such as agar, may have a melting point that is lower than the testing temperature.
During ablation, in particular RFA, it is important to monitor the temperature of the electrode to prevent ablation of unintended tissue areas and depths, and to prevent the electrode from overheating. Because thermochromic materials may provide visualization of minute temperature gradients, as well as binary threshold temperature confirmation, they are especially useful in the medical industry. Thermochromic materials and compounds may be used to indicate when an electrode reaches a certain threshold temperature. For example, binary thermochromic materials may be colored and opaque at room temperature, but become transparent when the threshold temperature is reached. Common uses for thermochromic materials include thermochromic thermometers, battery charge indicators, and color-change dyes. However, the use of thermochromic materials has not yet been adapted for use in the evaluation of such medical procedures as RFA.
To accurately evaluate the effectiveness of RFA and other ablation therapies, it is desired to provide a tissue phantom that could mimic a variety of mammalian tissues and that gives visual confirmation of the temperature gradient produced within the tissue phantom by the application of RF energy. Such a device and method of use would reduce variability in test setup and decrease overall testing time, allowing for a statistically significant number of tests to be conducted in less time than traditional testing methods.